In the case of timeshares, you can call the timeshare itself up and ask if Mr. and/or Ms. X is an owner for the week of Feb. 18-25, under the guise of being given permission to occupy the unit as their guest during their share-week.
I have had no problem with this and have done it 3x with success and have been very satisfied with the units I was able to use. But I have only dealt with well-established Silicon Valley owners of Lake Tahoe timeshares who had active paypal accounts.
Edit: all of the ads I responded to here were posted on SF bay craigslist.
